In many industrial installations, including coal mines, power stations, concrete mixing plants, and many others, it is necessary or desirable to move appreciable quantities of granular material from one location to another. For example, in a coal mine quantities of granular coal may need to be moved, often in two or more steps, from a mine face to a storage location for subsequent shipment to a coal consumer. In a power station utilizing granular coal for fuel, the coal is often initially stored at a site separate from the power generating installation and is subsequently delivered to that installation as needed. Similarly, the ash or other waste product produced by burning of the coal may require removal from the power generation facility to yet another separate location. In a concrete mixing plant a granular stone aggregate may be initially stored at a location remote from the mixing plant; in such an installation, the aggregate may be moved to the mixing plant when it is needed.
In these and many other industrial facilities a conveyor, usually a belt conveyor, is employed to transport the granular material (e.g., coal, granular stone aggregate, etc.) to or from the location at which it is utilized. Most such conveyors have an input chute for delivering the granular material to the conveyor and a discharge chute for discharge of the granular material at the output end of the conveyor. In either case, the chute often includes one or more impact surfaces on which the granular material impinges. Those impact surfaces are often subject to appreciable abrasion from the granular material, and hence present a continuing requirement for repair and/or replacement of the chute.
Prior proposals directed toward amelioration or correction of these and similar abrasion problems have included corrugations, formed in sheet metal or metal plates, to guide movement of the granular material. Multiple short knobs of molded metal have also been suggested. But prior proposals addressing this difficulty have generally been unduly expensive or have not fully met the abrasion problems presented.
Further, in the sizing of granular material such as coal, screen deck systems in a granule sizing machine or classification machine are used for receiving and sizing the coal. These screens are generally angularly disposed to receive a stream of coal or granular material from the discharge end of a conveyor. A screen impact surface for receiving the stream of coal or granular material is usually at the input end of the first or uppermost screen. Wear on the impact surface requires periodic replacement or repair of the screen.